Increasing the density of integrated circuits can increase speed and enable new applications. Many applications rely on the formation of gaps whose height-to-width aspect ratio increases with increasing density of the devices. The gaps are typically filled with a material appropriate for the specific application. The gapfill may be a conductor or a dielectric. In either case, a conformal liner may be needed prior to depositing the gapfill material. The conformal layer is intended to avoid undesirable diffusion or electrical leakage across the conformal liner either during manufacture or during the active life of the device. A high height-to-width aspect ratio gap makes applying a conformal liner difficult. The conformal liner should be uniform, relatively defect-free, and thin relative to the gap width.
Techniques which have been used to form conformal liners in gapfill applications are chemical-vapor deposition (“CVD”) or plasma-enhanced CVD (“PECVD”) techniques. CVD and PECVD methods may begin forming non-conformal liners and may deposit more material near the opening of a gap compared to down deep within the gap. Atomic Layer Deposition (ALD) may regain the desirable high conformality by alternating the exposure to precursors. However, the deposition rates typical for ALD are low and increase processing times.
Techniques are needed for forming very thin conformal liner layers for inhibiting diffusion and inhibiting electrical leakage while maintaining cost-effective deposition rates.